Effects of Intrathecal Dexmedetomidine-Bupivacaine versus Intravenous Dexmedetomidine Plus Intrathecal Bupivacaine: A Randomised Triple-blind Clinical Study

Introduction: For administering Spinal Anesthesia (SA) 0.5% bupivacaine is employed with Dexmedetomidine (DMT) as an adjuvant. Literature review reveals that either intrathecal or low-dose intravenous DMT can enhance the characteristics of SA with bupivacaine Aim: To evaluate the effect of a single bolus intravenous (i.v.) DMT 0.5 mu g/kg given either before or after the SA in combination with intrathecal 0.5% bupivacaine compared with intrathecal bupivacaine plus DMT. Materials and Methods: A randomised, triple-blind, single-centre and placebo-controlled study was conducted at Gayatri Vidyaparishad Institute of Health care and medical technology, Marikavalasa, Visakhapatnam, Andhra Pradesh, India, from April 2020 to December 2021. Eighty patients were allocated to four study groups of 20 each. Patients of group Intrathecal DMT (ITD) were given SA with 0.5% bupivacaine heavy 3.4 mL+5 mu g DMT, patients of group Before Spinal DMT (BSD) were given intravenous DMT before administering the SA with bupivacaine, patients of group After Spinal DMT (ASD) were given intravenous DMT after administering the SA with bupivacaine, and the patients of group Nil DMT (ND) or control group, were given SA with 0.5% bupivacaine heavy 3.4 mL. The primary outcome variable was the difference in the duration of analgesia. The secondary outcome variables were the differences in the onset and duration of the block both motor and sensory. Differences of the parametric data were analyzed using Analysis of Variance (ANOVA) and Tukey's Post Hoc test HSD Beta (Honestly significant difference). For analysis of non parametric data Chisquare test was used and a p-value of =0.05 was considered as statistically significant. Results: Patients in the ITD group had a longer duration of analgesia of 280.7 +/- 5.0 min (vis-a-vis 215 +/- 9.34, 210.7 +/- 12.0 and 97.9 +/- 7.12 min in BSD,ASD and ND, respectively) with a statistically significant difference at a p-value <0.00001. They had a shorter duration of onset of motor block of 3.4 +/- 0.49 (visa-vis 4.6 +/- 0.53, 6.09 +/- 0.44 and 6.3 +/- 0.65 in BSD, ASD and ND groups, respectively) with a statistically significant difference at a p-value <0.00001. Duration of onset of the sensory block was 2.2 +/- 0.37 min in the patients of ITD group (vis-a-vis 3.2 +/- 4.76, 3.5 +/- 6.71 and 4 +/- 0.40 in BSD,ASD and ND groups, respectively) with a statistically significant difference at a p-value <0.00001. Conclusion: Dexmedetomidine used as an adjuvant to intrathecal bupivacaine produces greater augmentation of duration of analgesia, earlier onset of sensory and motor block, more haemodynamic stability and fewer overall side effects compared to its intravenous bolus administration.